CS269595B1 - A method for removing unreacted hydroxyarenes from an alkylase mixture - Google Patents

Abstract

The essence of the solution is a method of removing unreacted hydroxyarene and low molecular weight alkylhydroxyarenes from the reaction mixture by desorption with water vapor, nitrogen or a combination thereof at a temperature of 383 to 453 K, preferably 413 to 423 K.

Description

The invention relates to a method for removing unreacted hydroxyarenes and low molecular weight alkyl-hydroxyarenes in a reaction mixture after alkylation of hydroxyarenes with alkenes and oligomers of olefins with an average degree of polymerization of 5 to 5θ.

In the production of polymer stabilizers with antioxidant effect, hydroxyarenes are first alkylated with alkenes and olefin oligomers. Various modification-alkylations are known and described in a number of protected processes, e.g. Czech Patent Application No. 174 679, Czech Patent Application No. 226 912. In Salšy, the alkylation mixture is freed from the catalyst by filtration.

Unreacted hydroxyarene and low molecular weight alkyl-hydroxyarenes are removed from the alkylation mixture according to the above-mentioned Cs AO and according to Čs AO 223 060; AO 211 775; AO 213 093; Salej by distillation at a pressure of 0.2 - 5 kPa and a temperature of 393 - 573 K. Since colored impurities are formed during distillation under the above conditions, the product must be subsequently refined, for example with bleaching earth (BH). After filtering off the refining agent, a product is obtained that has a color intensity of more than 500 Bazen units.

Currently, in the production of an antioxidant based on alkylated 2,6 xylenol, the method described in Czech Patent Application No. AO 223 060 is used to remove unreacted 2,6-dimethylhydroxybenzene and low-molecular-weight 4-alkyl 2,6-dimethylhydroxybenzenes, the essence of which is the distillation of the aforementioned hydroxyarenes on a film rotary evaporator.

The biggest disadvantage of the method used is that, as a result of thermal stress in the evaporator, the product degrades, colored impurities appear, and the product must always be subsequently refined, which represents a loss of the finished product in the refining agent.

Another disadvantage is that during distillation under vacuum of 2-4 kPa, if the vacuum suddenly drops due to faults (leaks, pump failure, etc.), there is insufficient separation of unwanted substances and even a small overspray causes an increase in the content of unreacted hydroxyarene in the product above the required value of 0.1 wt. %. The entire separation process must then be repeated.

The disadvantages of the previous processes are eliminated by the process according to the invention. Its subject is a method for treating the alkylate from the alkylation of hydroxyarenes with alkenes and olefin oligomers with an average degree of polymerization of 5 to 50, characterized in that unreacted hydroxyarenes and low molecular weight alkylhydroxyarenes are removed from the alkylation mixture by desorption with water vapor and/or inert gas at a temperature of 383 to 453 K, preferably 413 to 423 K.

The process according to the invention can be carried out in a semi-continuous or continuous manner. In both methods, the alkylation mixture, freed from the catalyst by filtration, is dosed to the head of the desorption column. Water vapor is fed to the lower part either alone or in combination with an inert gas, which may be nitrogen, carbon dioxide or waste gas with a high proportion of inert components. In the semi-continuous method, the treated alkylate is returned to the storage vessel after passing through the column and is recirculated until the content of hydroxyarenes and low molecular weight alkylhydroxyarenes falls below 0.10% by weight. In the continuous method, the conditions (temperature, flow rate ratio of the desorption medium and the treated alkylate) are set in the desorption column so that the product leaving the bottom of the column does not contain unreacted hydroxyarenes and low molecular weight alkylhydroxyarenes above the prescribed concentration.

The procedure can be advantageously carried out in a packed or tray column. All industrially used organized and/or unorganized types of column packing can be used as packing. It is advantageous to use packing that allows achieving a large interfacial surface per unit volume of the apparatus. In doing so, it is necessary to maintain the rules for selecting the size of the packing depending on the diameter of the column and to observe the required hydraulic regime. It is less advantageous to carry out desorption in a heated boiler, into which the desorption agent is fed through a distributor. In this case, increased investment costs will be required due to the larger interfacial surface.

CS 269 595 Bl

The main advantage of the process according to the invention is the removal of unreacted impurities at a lower temperature. In this method, the formation of color impurities is significantly limited. The product prepared by the process according to the invention is weakly colored, its color is a maximum of 500 Pool units. Another advantage is that the need for additional irradiation is eliminated, with a subsequent reduction in investment and operating costs and prevention of product losses.

The procedure is illustrated by the following examples:

Example 1

The alkylate is injected into the upper part of a heated glass desorption column with a diameter of 0.03 rc and a height of 0.35 m filled with Berl saddles of size 0.006 m at a rate of 3.5 ml.min ^-1 and a temperature of 413 K. The alkylate contains 3.9 wt. % free 2,6-xylenol and 12.31 wt. % bound 2,6-xylenol. Steam is fed into the lower part of the column at a rate of 9 to 10 g.min~l at a temperature of 413 K together with a small amount of nitrogen 0.2 l.min ^- ^, which ensures an inert atmosphere in the product collection vessel. The steam bubbles through the flowing alkylate and is enriched with unreacted 2,6-xylenol and low-molecular alkyl 2,6-xylenols, light fractions of the alkene fraction used as an alkylating agent. The vapors from the column head are condensed in a condenser. In a separator, the organic phase is separated from the condensed water. The organic phase contains 62 wt. % of total 2,6 xylenol, the remainder being the heavy fractions of the alkene fraction used as an alkylating agent. 0.53 wt. % of 2,6 xylenol was determined in the aqueous layer. The product in an amount of 3.1 ml.min”}· emerges from the bottom of the column. The composition of the product is 0.02 wt. % of free 2,6 xylenol and 9.7 wt. % of bound 2,6 xylenol. Its color intensity is less than 500 Pool units.

Example 2

300 g of alkylate was heated in a flask under a nitrogen atmosphere to a temperature of 523 K. The alkylate contained 5.6 wt. % free 2,6 xylenol and 6.95 wt. % bound 2,6 xylenol. Steam was fed from a steam generator to the bottom of the flask at a temperature of 413 K. The escaping vapors were condensed in a condenser. The condensate was separated into two phases, aqueous and organic. The organic phase contained 59.2 wt. % 2,6 xylenol, the remainder being light portions of the alkylating agent. 450 g of water vapor was used for desorption. The product obtained was slightly yellow, the color below 500 Bazen units.

Example 3

300 g of alkylate containing catalyst BH was heated in a flask under nitrogen to 423 K. The alkylate contained 3.06 wt. % free 2,6 xylenol and 10.76 wt. % bound 2,6 xylenol. Steam was introduced to the bottom of the flask at a temperature of 413 to 423 K. 450 g of water vapor was used for desorption. The final product obtained after filtering off BB contained 0.053 wt. % free 2,6 xylenol and 10.01 wt. % bound 2,6 xylenol. The color intensity of the product was 500 Bazen units.

Claims (1)

The main advantage of the process according to the invention is the centrifugation of non-reactive substances. temperature. In this process, the formation of color grades is substantially reduced. The product of the present invention is weakly vivid, its color is at most 500 Hazen Units. Another advantage is that the need for long-term radiation is eliminated, with consequent reduction in investment and operating costs and product avoidance. The process is illustrated by the following examples: EXAMPLE 1 Into a top of a heated glass desorption column having a diameter of 0.03 rc and a height of 0.35 m filled with a paddle of 0.006 m, an alkylate of 3.5 ml.min-1 is sprayed. and 413 K. The alkylate contains 3.9 wt. free 2.6 xylenol and 12.31 wt. % bound xylenol. Steam is fed to the bottom of the column at a rate of 9 to 10 g / min at 413 K, along with a small amount of nitrogen of 0.2 l / min to provide an inert atomosphere in the product collector. The steam-bubbling alkylate and enriched with unreacted 2,6 xylenol and low molecular weight 2,6-xylenols, light portions of the alkene fraction used as alkylating agent. Separate the organic phase from the condensed water. The organic phase contains 62 wt. % of the total 2.6 xylenol, the light weight fraction of the alkene fraction used as the alkylating agent. 0.53 wt. % 2.6 xylenol. The product, 3.1 ml / min, exits the bottom of the column. The composition of the product is 0.02 wt. % free 2.6 xylenol and 9.7 wt. % bound xylenol. Its color intensity is less than 500 Hazen units. EXAMPLE 2 300 g of alkylate were heated to 523 K in a nitrogen atmosphere flask. % free 2.6 xylenol and 6.95 wt. % bound xylenol. Steam was fed to the bottom of the flask at 413 K from the steam generator. The condensate was divided into two phases, aqueous and organic. The organic phase contained 59.2 wt. % Of 2.6 xylenol, the remainder being the light weight of the alkylating agent. 450 g of water vapor were used for desorption. The product obtained was poorly colored, coloring below 500 Hazen units. EXAMPLE 3 300 g of the BH-containing catalyst-containing alkylate were heated to 423 K in a nitrogen atmosphere. The alkylate contained 3.06 wt. % free 2.6 xylenol and 10.76 wt. % bound xylenol. Steam is fed to the bottom of the flask at 413 to 423K. The final product obtained after filtration of BH contained 0.053 wt. % free 2.6 xylenol and 10.01 wt. % bound xylenol. The color intensity of the product was 500 Hazen units. OBJECT OF THE INVENTION A process for the alkylation of hydroxyarenes by alkylation with olefins and olefin oligomers with an intermediate polymerization step 5 to 50, wherein unreacted hydroxyarenes and low molecular weight alkylhydroxyarenes are removed from the alkylation mixture by desorption steam and / or inert gas at a temperature of 383 to 453 K, s. preferably 413 to 423 K.